The long-term goal of the proposed program is to overcome the problem of immunologic rejection of therapeutic tissue and organ transplants in patients. Thus far this program has pertained almost entirely to renal transplantation. The main research aims are: (1) to apply advances in basic immunogenetics research to therapeutic tissue and organ transplantation in patients; (2) to improve thereby the success rate of such treatment; and (3) to utilize materials and information derived from patients to contribute to further immunogenetic advances. Emphasis presently is on utilizing leukocyte typing and other methods of histocompatibility testing and developing these methods to their full potential of clinical usefulness in the selection of compatible donors. Further advances in histocompatibility testing and in immunosuppression may lead to practical means of establishing specific immunologic tolerance in man, which in some respects might be regarded the ultimate and ideal means of avoiding immunologic rejection. A number of nonimmunologic studies of patients in this program also are being pursued particularly in the fields of urology, nephrology psychiatry, pathology, renal physiology, and microbiology.